Diffing a subject replayable execution trace against a plurality of comparison replayable execution traces

ABSTRACT

Diffing a subject replayable trace against a plurality of comparison replayable traces includes identifying a set of mappings among the comparison replayable traces, each identifying corresponding comparison sections of consecutive instructions recorded in the comparison replayable traces that execute equivalently. A plurality of distinct comparison sections are identified within the comparison replayable traces. Each of a plurality of subject sections within the subject trace is compared against distinct comparison section(s) to determine a comparison status for each subject section, including whether each subject section is (i) equal to at least one corresponding distinct comparison section, or (ii) different than the distinct comparison sections. The determined comparison status of at least one particular subject section with respect at least one particular corresponding distinct comparison section is applied to each additional comparison section to which the at least one particular distinct comparison section is mapped in the set of mappings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related by subject matter to (Docket Nos. 1368.3817/407762-US-NP), titled “DIFFING A SUBJECT REPLAYABLE EXECUTION TRACE AGAINST A COMPARISON REPLAYABLE EXECUTION TRACE,” and (Docket Nos. 1368.3819/407760-US-NP), titled, “DIFFING A PLURALITY OF SUBJECT REPLAYABLE EXECUTION TRACES AGAINST A PLURALITY OF COMPARISON REPLAYABLE EXECUTION TRACES,” each of which is filed concurrently herewith.

BACKGROUND

Tracking down and correcting undesired software behaviors is a core activity in software development. Undesired software behaviors can include many things, such as execution crashes, runtime exceptions, slow execution performance, incorrect data results, data corruption, and the like. Undesired software behaviors might be triggered by a vast variety of factors such as data inputs, user inputs, race conditions (e.g., when accessing shared resources), etc. Given the variety of triggers, undesired software behaviors can be rare and seemingly random, and extremely difficult reproduce. As such, it can be very time-consuming and difficult for a developer to identify a given undesired software behavior. Once an undesired software behavior has been identified, it can again be time-consuming and difficult to determine its root cause(s).

Developers have conventionally used a variety of approaches to identify undesired software behaviors, and to then identify the location(s) in an application's code that cause the undesired software behavior. For example, a developer might test different portions of an application's code against different inputs (e.g., unit testing). As another example, a developer might reason about execution of an application's code in a debugger (e.g., by setting breakpoints/watchpoints, by stepping through lines of code, etc. as the code executes). As another example, a developer might observe code execution behaviors (e.g., timing, coverage) in a profiler. As another example, a developer might insert diagnostic code (e.g., trace statements) into the application's code.

While conventional diagnostic tools (e.g., debuggers, profilers, etc.) have operated on “live” forward-executing code, an emerging form of diagnostic tools enable “historic” debugging (also referred to as “time travel” or “reverse” debugging), in which the execution of at least a portion of a program's thread(s) is recorded into one or more trace files (i.e., an execution trace). Using some tracing techniques, an execution trace can contain “bit-accurate” historic execution trace data, which enables the recorded portion(s) the traced thread(s) to be virtually “replayed” (e.g., via emulation) down to the granularity of individual instructions (e.g., machine code instructions, intermediate language code instructions, etc.). Thus, using “bit-accurate” trace data, diagnostic tools can enable developers to reason about a recorded prior execution of subject code, as opposed to a “live” forward execution of that code. For example, using execution traces, a historic debugger might provide user experiences that enable both forward and reverse breakpoints/watchpoints, that enable code to be stepped through both forwards and backwards, etc. A historic profiler, on the other hand, might be able to derive code execution behaviors (e.g., timing, coverage) from prior-executed code.

Since modern microprocessors commonly execute at the rate of tens- to hundreds-of thousands of MIPS (millions of instructions per second), execution traces can capture vast amounts of information, even if the capture mere fractions of a second of a thread's execution. As such, analyzing and presenting information about execution traces can present significant technical hurdles.

BRIEF SUMMARY

At least some embodiments described herein diff replayable execution traces. This can include diffing a single subject execution trace against a single comparison execution trace (e.g., 1:1), diffing a single subject execution trace against a plurality of comparison execution traces (e.g., 1:N), and/or diffing a plurality of subject execution traces against a plurality of comparison execution traces (e.g., M:N). The embodiments herein operate by grouping sequences of related executable instructions, and performing diffing based on attributes of those groups to determine if the groups executed equivalently, even if the particular instructions in those groups differed. Thus, the embodiments herein can diff sets of traced instructions, even where those instructions executed from applications having different binaries (e.g., due code changes, compiler changes, compiler settings changes, processor Instruction Set Architecture (ISA) changes, and the like). In addition, the embodiments herein can diff different sections of traced instructions at different levels of detail, enabling processing resources to be devoted to those areas of particular interest.

In some embodiments, methods, systems, and computer program products for diffing a subject replayable execution trace against a comparison replayable execution trace access a first subject replayable execution trace which represents a first sequence of executable instructions that executed as part of a first executing entity, and a second comparison replayable execution trace which represents a second sequence of executable instructions that executed as part of a second executing entity. These embodiments also identify a first plurality of functions within the first sequence of executable instructions, and a second plurality of functions within the second sequence of executable instructions. Each function corresponds to a sequence of one or more executable instructions that executed as part of the function. These embodiments also identify a first plurality of groups of the first plurality of functions, and a second plurality of groups of the second plurality of functions. Each group comprises a sequence of one or more related functions. These embodiments also compare the first plurality of groups and the second plurality of groups. The comparison includes determining, based on an identity of each group and on one or more functions corresponding to the group, if each first group in the first plurality of groups is at least one of equal to a second group in the second plurality of groups, a replacement of a second group in the second plurality of groups, deleted from the second plurality of groups, or inserted into the second plurality of groups. These embodiments also provide one or more indicia of a result of the comparing to a software component at the computer system, or to another computer system. The indicia indicate whether each first group is at least one of equal to a second group in the second plurality of groups, a replacement of a second group in the second plurality of groups, deleted from the second plurality of groups, or inserted into the second plurality of groups.

In other embodiments, methods, systems, and computer program products for diffing a subject replayable execution trace against a plurality of comparison replayable execution traces access a subject replayable execution trace, and a plurality of comparison replayable execution traces. Each replayable execution trace represents a corresponding sequence of executable instructions that executed as part of a corresponding executing entity. These embodiments also identify a set of mappings among the plurality of comparison replayable execution traces. Each mapping identifies two or more corresponding comparison sections of consecutive executable instructions within the plurality of comparison replayable execution traces that execute equivalently. Each comparison section in each mapping is from a different one of the plurality of comparison replayable execution traces. Based on the set of mappings, these embodiments also identify a plurality of distinct comparison sections within the plurality of comparison replayable execution traces. Each distinct comparison section either (i) lacks a mapping in the set of mappings, or (ii) is a representative comparison section from a different mapping in the set of mappings. These embodiments also compare the subject replayable execution trace and the plurality of comparison replayable execution traces. The comparing includes comparing each of a plurality of subject sections of consecutive executable instructions within the subject execution trace against one or more of the plurality of distinct comparison sections. Based on the comparing, these embodiments also determine a comparison status of each of the plurality of subject sections. The determining includes determining at least one of whether each subject section is (i) equal to at least one corresponding distinct comparison section, or (ii) different than the plurality of distinct comparison sections. The determined comparison status of at least one particular subject section with respect at least one particular corresponding distinct comparison section is applied to each additional comparison section to which the at least one particular distinct comparison section is mapped in the set of mappings. These embodiments also provide an indicia of a result of the determining to a software component at the computer system, or to another computer system.

In yet other embodiments, methods, systems, and computer program products for diffing a plurality of subject replayable execution traces against a plurality of comparison replayable execution traces access a plurality of subject replayable execution traces, and a plurality of comparison replayable execution traces. Each replayable execution trace represents a corresponding sequence of executable instructions that executed as part of a corresponding executing entity. For the plurality of subject replayable execution traces, these embodiments identify a first set of mappings among the plurality of subject replayable execution traces and, based on the first set of mappings, and identify a plurality of distinct subject sections within the plurality of subject replayable execution traces. Each mapping of the first set of mappings identifies two or more corresponding subject sections of consecutive executable instructions within the plurality of subject replayable execution traces that execute equivalently, and each subject section in each mapping is from a different one of the plurality of subject replayable execution traces. Each distinct subject section either (i) lacks a mapping in the first set of mappings, or (ii) is a representative subject section from a different mapping in the first set of mappings. For the plurality of comparison replayable execution traces, these embodiments identify a second set of mappings among the plurality of comparison replayable execution traces and, based on the second set of mappings, identify a plurality of distinct comparison sections within the plurality of comparison replayable execution traces. Each mapping of the second set of mappings identifies two or more corresponding comparison sections of consecutive executable instructions within the plurality of comparison replayable execution traces that execute equivalently, and each comparison section in each mapping is from a different one of the plurality of comparison replayable execution traces. Each distinct comparison section either (i) lacks a mapping in the second set of mappings, or (ii) is a representative comparison section from a different mapping in the second set of mappings. These embodiments also compare the plurality of subject replayable execution traces and the plurality of comparison replayable execution traces. The comparing includes comparing each of the plurality of distinct subject sections against one or more of the plurality of distinct comparison sections. Based on the comparing, these embodiments determine a comparison status of each of the plurality of distinct subject sections. The determining includes determining at least one of whether each distinct subject section is (i) equal to at least one corresponding distinct comparison section, or (ii) different than the plurality of distinct comparison sections. The determined comparison status of at least one particular distinct subject section with respect at least one particular corresponding distinct comparison section is applied to (i) each additional comparison section to which the at least one particular distinct comparison section is mapped in the second set of mappings, and to (ii) each additional subject section to which the at least one particular distinct subject section is mapped in the first set of mappings. The embodiments also provide an indicia of a result of the determining to a software component at the computer system, or to another computer system.

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and other advantages and features of the invention can be obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

FIG. 1A illustrates an example computing environment that facilitates diffing replayable execution traces;

FIG. 1B illustrates an example debugging component that diffs replayable execution traces;

FIG. 2 illustrates an example computing environment in which the computer system of FIG. 1A is connected to one or more other computer systems over one or more networks;

FIG. 3 illustrates an example of a recorded execution of an executable entity;

FIG. 4A illustrates two sequences of recorded executable instructions for diffing by a debugging component;

FIG. 4B illustrates groupings of the executable instructions of FIG. 4A into sections of related consecutive executable instructions;

FIG. 4C illustrates further grouping the sections of consecutive executable instructions illustrated in FIG. 4B into higher-level groups;

FIG. 5A illustrates an example differencing notation for the higher-level groups of FIG. 4C;

FIG. 5B illustrates an example of group comparison status based on the differencing notations of FIG. 5A;

FIG. 5C illustrates an example of utilizing code emulation and inputs/outputs comparison to determine if functions on different traced instruction sequences executed equivalently;

FIG. 5D illustrates an example of utilizing code emulation and inputs/outputs comparison to determine if functions on different traced instruction sequences executed equivalently;

FIG. 6 illustrates a flow chart of an example method for diffing a subject replayable execution trace against a comparison replayable execution trace;

FIG. 7A illustrates an example of one to many (1:N) trace comparison;

FIG. 7B illustrates an example of one to many (1:N) trace comparison, including partial traces;

FIG. 7C illustrates an example of many to many (M:N) trace comparison;

FIG. 7D illustrates an example of many to many (M:N) trace comparison, including partial traces;

FIG. 8 illustrates a flow chart of an example method for diffing a subject replayable execution trace against a plurality of comparison replayable execution traces; and

FIG. 9 illustrates a flow chart of an example method for diffing a plurality of subject replayable execution traces against a plurality of comparison replayable execution traces.

DETAILED DESCRIPTION

At least some embodiments described herein diff replayable execution traces. This can include diffing a single subject execution trace against a single comparison execution trace (e.g., 1:1), diffing a single subject execution trace against a plurality of comparison execution traces (e.g., 1:N), and/or diffing a plurality of subject execution traces against a plurality of comparison execution traces (e.g., M:N). The embodiments herein operate by grouping sequences of related executable instructions, and performing diffing based on attributes of those groups to determine if the groups executed equivalently, even if the particular instructions in those groups differed. Thus, the embodiments herein can diff sets of traced instructions, even where those instructions executed from applications having different binaries (e.g., due code changes, compiler changes, compiler settings changes, processor ISA changes, and the like). In addition, the embodiments herein can diff different sections of traced instructions at different levels of detail, enabling processing resources to be devoted to those areas of particular interest.

An execution trace used by the embodiments herein might be generated by a variety of historic debugging technologies. In general, historic debugging technologies record or reconstruct the execution state of an entity at various times, in order to enable execution of that entity to be at least partially re-executed or emulated later from that execution state. The fidelity of that virtual execution varies depending on what traced execution state is available.

For example, one class of historic debugging technologies, referred to herein as time-travel debugging, continuously records a bit-accurate trace of an entity's execution. This bit-accurate trace can then be used later to faithfully replay that entity's prior execution down to the fidelity of individual code instructions. For example, a bit-accurate trace might record information sufficient to reproduce initial processor state for at least one point in a thread's prior execution (e.g., by recording a snapshot of processor registers), along with the data values that were read by the thread's instructions as they executed after that point in time (e.g., the memory reads). This bit-accurate trace can then be used to replay execution of the thread's code instructions (starting with the initial processor state) based on supplying the instructions with the recorded reads.

Another class of historic debugging technology, referred to herein as branch trace debugging, relies on reconstructing at least part of an entity's execution state based on working backwards from a dump or snapshot (e.g., a crash dump of a thread) that includes a processor branch trace (i.e., which includes a record of whether or not branches were taken). These technologies start with values (e.g., memory and register) from this dump or snapshot and, using the branch trace to at least partially determine code execution flow, iteratively replay the entity's code instructions and backwards and forwards in order to reconstruct intermediary data values (e.g., register and memory) used by this code until those values reach a steady state. These techniques may be limited in how far back they can reconstruct data values, and how many data values can be reconstructed. Nonetheless, the reconstructed historical execution data can be used for historic debugging.

Yet another class of historic debugging technology, referred to herein as replay and snapshot debugging, periodically records full snapshots of an entity's memory space and processor registers while it executes. If the entity relies on data from sources other than the entity's own memory, or from a non-deterministic source, these technologies might also record such data along with the snapshots. These technologies then use the data in the snapshots to replay the execution of the entity's code between snapshots.

FIG. 1A illustrates an example computing environment 100 that facilitates diffing replayable execution traces. As depicted, computing environment 100 may comprise or utilize a special-purpose or general-purpose computer system 101, which includes computer hardware, such as, for example, one or more processors 102, system memory 103, durable storage 104, and/or network device(s) 105, which are communicatively coupled using one or more communications buses 106.

Embodiments within the scope of the present invention can include physical and other computer-readable media for carrying or storing computer-executable instructions and/or data structures. Such computer-readable media can be any available media that can be accessed by a general-purpose or special-purpose computer system. Computer-readable media that store computer-executable instructions and/or data structures are computer storage media. Computer-readable media that carry computer-executable instructions and/or data structures are transmission media. Thus, by way of example, and not limitation, embodiments of the invention can comprise at least two distinctly different kinds of computer-readable media: computer storage media and transmission media.

Computer storage media are physical storage media (e.g., system memory 103 and/or durable storage 104) that store computer-executable instructions and/or data structures. Physical storage media include computer hardware, such as RAM, ROM, EEPROM, solid state drives (“SSDs”), flash memory, phase-change memory (“PCM”), optical disk storage, magnetic disk storage or other magnetic storage devices, or any other hardware storage device(s) which can be used to store program code in the form of computer-executable instructions or data structures, which can be accessed and executed by a general-purpose or special-purpose computer system to implement the disclosed functionality of the invention.

Transmission media can include a network and/or data links which can be used to carry program code in the form of computer-executable instructions or data structures, and which can be accessed by a general-purpose or special-purpose computer system. A “network” is defined as one or more data links that enable the transport of electronic data between computer systems and/or modules and/or other electronic devices. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a computer system, the computer system may view the connection as transmission media. Combinations of the above should also be included within the scope of computer-readable media.

Further, upon reaching various computer system components, program code in the form of computer-executable instructions or data structures can be transferred automatically from transmission media to computer storage media (or vice versa). For example, computer-executable instructions or data structures received over a network or data link can be buffered in RAM within a network interface module (e.g., network device(s) 105), and then eventually transferred to computer system RAM (e.g., system memory 103) and/or to less volatile computer storage media (e.g., durable storage 104) at the computer system. Thus, it should be understood that computer storage media can be included in computer system components that also (or even primarily) utilize transmission media.

Computer-executable instructions comprise, for example, instructions and data which, when executed at one or more processors, cause a general-purpose computer system, special-purpose computer system, or special-purpose processing device to perform a certain function or group of functions. Computer-executable instructions may be, for example, machine code instructions (e.g., binaries), intermediate format instructions such as assembly language, or even source code.

Those skilled in the art will appreciate that the invention may be practiced in network computing environments with many types of computer system configurations, including, personal computers, desktop computers, laptop computers, message processors, hand-held devices, multi-processor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, mobile telephones, PDAs, tablets, pagers, routers, switches, and the like. The invention may also be practiced in distributed system environments where local and remote computer systems, which are linked (either by hardwired data links, wireless data links, or by a combination of hardwired and wireless data links) through a network, both perform tasks. As such, in a distributed system environment, a computer system may include a plurality of constituent computer systems. In a distributed system environment, program modules may be located in both local and remote memory storage devices.

Those skilled in the art will also appreciate that the invention may be practiced in a cloud computing environment. Cloud computing environments may be distributed, although this is not required. When distributed, cloud computing environments may be distributed internationally within an organization and/or have components possessed across multiple organizations. In this description and the following claims, “cloud computing” is defined as a model for enabling on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services). The definition of “cloud computing” is not limited to any of the other numerous advantages that can be obtained from such a model when properly deployed.

A cloud computing model can be composed of various characteristics, such as on-demand self-service, broad network access, resource pooling, rapid elasticity, measured service, and so forth. A cloud computing model may also come in the form of various service models such as, for example, Software as a Service (“SaaS”), Platform as a Service (“PaaS”), and Infrastructure as a Service (“IaaS”). The cloud computing model may also be deployed using different deployment models such as private cloud, community cloud, public cloud, hybrid cloud, and so forth.

Some embodiments, such as a cloud computing environment, may comprise a system that includes one or more hosts that are each capable of running one or more virtual machines. During operation, virtual machines emulate an operational computing system, supporting an operating system and perhaps one or more other applications as well. In some embodiments, each host includes a hypervisor that emulates virtual resources for the virtual machines using physical resources that are abstracted from view of the virtual machines. The hypervisor also provides proper isolation between the virtual machines. Thus, from the perspective of any given virtual machine, the hypervisor provides the illusion that the virtual machine is interfacing with a physical resource, even though the virtual machine only interfaces with the appearance (e.g., a virtual resource) of a physical resource. Examples of physical resources including processing capacity, memory, disk space, network bandwidth, media drives, and so forth.

As shown in FIG. 1A, each processor 102 can include (among other things) one or more processing units 107 (e.g., processor cores) and one or more caches 108. Each processing unit 107 loads and executes machine code instructions via the caches 108. During execution of these machine code instructions at one more execution units 107 b, the instructions can use internal processor registers 107 a as temporary storage locations and can read and write to various locations in system memory 103 via the caches 108. In general, the caches 108 temporarily cache portions of system memory 103; for example, caches 108 might include a “code” portion that caches portions of system memory 103 storing application code, and a “data” portion that caches portions of system memory 103 storing application runtime data. If a processing unit 107 requires data (e.g., code or application runtime data) not already stored in the caches 108, then the processing unit 107 can initiate a “cache miss,” causing the needed data to be fetched from system memory 103—while potentially “evicting” some other data from the caches 108 back to system memory 103.

As illustrated, the durable storage 104 can store computer-executable instructions and/or data structures representing executable software components; correspondingly, during execution of this software at the processor(s) 102, one or more portions of these computer-executable instructions and/or data structures can be loaded into system memory 103. For example, the durable storage 104 is shown as potentially storing computer-executable instructions and/or data structures corresponding to a debugging component 109, a tracer component 110, an emulation component 111, and one or more application(s) 112. The durable storage 104 can also store data, such as at least one execution trace 113 (e.g., generated using one or more of the historic debugging technologies described above).

In general, the debugging component 109 leverages the emulation component 111 in order to emulate execution of code of executable entities, such as application(s) 112, based on execution state data obtained from at least one execution trace 113. Thus, FIG. 1A shows that the debugging component 109 and the emulation component 111 are loaded into system memory 103 (i.e., debugging component 109′ and emulation component 111′), and that the application(s) 112 are being emulated within the emulation component 111′ (i.e., application(s) 112′). As will be explained in more detail in connection with FIG. 1B, the debugging component 109 can provide functionality for diffing replayable execution traces. The debugging component 109 can correspond to any type of tool that consumes an execution trace 113 as part of analyzing a prior execution of an application 112. For instance, the debugging component 109 might be a debugger, a profiler, a cloud service, etc.

In general, the tracer component 110 records or “traces” execution of one or more of application(s) 112 into at least one execution trace 113 (e.g., using one or more types of the historic debugging technologies described above). The tracer component 110 can record execution of application(s) 112 whether that execution be a “live” execution on the processor(s) 102 directly, whether that execution be a “live” execution on the processor(s) 102 via a managed runtime, and/or whether that execution be an emulated execution via the emulation component 111. Thus, FIG. 1A also shows that the tracer component 110 is also loaded into system memory 103 (i.e., tracer component 110′). An arrow between tracer component 110′ and execution trace 113′ indicates that the tracer component 110′ can record trace data into execution trace 113′ (which might then be persisted to the durable storage 104 as execution trace 113).

Computer system 101 might additionally, or alternatively, receive at least one execution trace 113 from another computer system (e.g., using network device(s) 105). For example, FIG. 2 illustrates an example computing environment 200 in which computer system 101 of FIG. 1A is connected to one or more other computer systems 202 (i.e., computer systems 202 a-202 n) over one or more networks 201. As shown in example 200, each computer system 202 includes a tracer component 110 and application(s) 112. As such, computer system 101 may receive, over the network(s) 201, at least one execution trace 113 of at least one prior execution of one or more of application(s) 112 at these computer system(s) 202.

It is noted that, while the debugging component 109, the tracer component 110, and/or the emulation component 111 might each be independent components or applications, they might alternatively be integrated into the same application (such as a debugging suite), or might be integrated into another software component—such as an operating system component, a hypervisor, a cloud fabric, etc. As such, those skilled in the art will also appreciate that the invention may be practiced in a cloud computing environment of which computer system 101 is a part. For instance, while these components 109-111 might take the form of one or more software applications executed at a user's local computer, they might also take the form of a service provided by a cloud computing environment.

It was mentioned previously that the debugging component 109 can provide functionality for diffing replayable execution traces. To demonstrate how the debugging component 109 might accomplish the foregoing, FIG. 1B illustrates additional detail of the debugging component 109 of FIG. 1A. The depicted debugging component 109 in FIG. 1B includes a variety of components (e.g., data access 114, grouping 115, alignment 116, diffing 117, output 118, etc.) that represent various functions that the debugging component 109 might implement in accordance with various embodiments described herein. It will be appreciated that the depicted components—including their identity, sub-components, and arrangement—are presented merely as an aid in describing various embodiments of the debugging component 109 described herein, and that these components are non-limiting to how software and/or hardware might implement various embodiments of the debugging component 109 described herein, or of the particular functionality thereof.

As shown, the data access component 114 includes a trace access component 114 a and a code access component 114 b. The trace access component 114 a accesses execution traces, such as an execution trace 113 of a prior execution of application 112. FIG. 3 illustrates one example of an execution trace 300 of an executable entity (e.g., application 112) that might be accessed by the trace access component 114 a, where the execution trace 300 might have been generated using time-travel debugging technologies. Note that execution trace 300 is one example, only and that traces could take a variety of formats, so long as they provide way to recover each thread from the recording. Notably, the term “thread” should be treated generally herein to refer to any linear execution of code, even if that code were to be dispatched by multiple separate operating system threads.

In the example of FIG. 3, execution trace 300 includes a plurality of data streams 301 (i.e., data streams 301 a-301 n). In embodiments, each data stream 301 represents execution of a different thread that executed from the code of an application 112. For example, data stream 301 a might record execution of a first thread of application 112, while data stream 301 n records an n^(th) thread of application 112. As shown, data stream 301 a comprises a plurality of data packets 302. Since the particular data logged in each data packet 302 might vary, they are shown as having varying sizes. In general, when using time-travel debugging technologies, a data packet 302 might record the inputs (e.g., register values, memory values, etc.) to one or more executable instructions that executed as part of this first thread of application 112. As shown, data stream 301 a might also include one or more key frames 303 (e.g., key frames 303 a and 303 b) that each records sufficient information, such as a snapshot of register and/or memory values, that enables the prior execution of the thread to be replayed by the emulation component 111, starting at the point of the key frame and proceeding forward.

In embodiments, an execution trace 113 might also include the actual code that was executed as part of an application 112. Thus, in FIG. 3, each data packet 302 is shown as including a non-shaded data inputs portion 304 and a shaded code portion 305. In embodiments, the code portion 305 of each data packet 302, if present, might include the executable instructions that executed based on the corresponding data inputs. In other embodiments, however, an execution trace 113 might omit the actual code that was executed, instead relying on having separate access to the code of the application 112 (e.g., from durable storage 104). In these other embodiments, each data packet may, for example, specify an address or offset to the appropriate executable instruction(s) in an application binary image. Although not shown, it may also be possible that the execution trace 300 includes a data stream 301 that stores one or more of the outputs of code execution. It is noted that used of different data input and code portions of a data packet is for illustrative purposes only, and that the same data could be stored in a variety of manners, such as by the use of multiple data packets.

If there are multiple data streams 301, each recording execution of a different thread, these data streams might include sequencing events. Each sequencing event records the occurrence of an event that is orderable across the threads. For example, sequencing events might correspond to interactions between the threads, such as accesses to memory that is shared by the threads. Thus, for instance, if a first thread that is traced into a first data stream (e.g., 301 a) writes to a synchronization variable, a first sequencing event might be recorded into that data stream (e.g., 301 a). Later, if a second thread that is traced into a second data stream (e.g., 301 b) reads from that synchronization variable, a second sequencing event might be recorded into that data stream (e.g., 301 b). These sequencing events might be inherently ordered. For example, each sequencing event might be associated with a monotonically incrementing value, with the monotonically incrementing values defining a total order among the sequencing events. For instance, a first sequencing event recorded into a first data stream might be given a value of one, a second sequencing event recorded into a second data stream might be given a value of two, etc.

Returning to FIG. 1B, the code access component 114 b might obtain the code of application 112. If the execution trace(s) 113 obtained by the trace access component 114 a included the traced code (e.g., code portion 305), then the code access component 114 b might extract that code from an execution trace 113. Alternatively, the code access component 114 b might obtain the code of application 112 from the durable storage 104 (e.g., from an application binary image).

The grouping component 115 identifies logical groupings (or sections) of sequences of prior-executed executable instructions whose execution is recorded in the traces accessed by the trace access component 114 a. In embodiments, the grouping component 115 takes advantage of the fact that executable code is usually organized into logical structures (e.g., libraries, modules, namespaces, classes, functions, etc.) to identify groupings/sections of consecutive executable instructions that are logically related. For example, a sequence of instructions may belong to a corresponding function, class, module, etc. Since executable code can often be organized hierarchically, in embodiments the grouping component 115 can identify hierarchical arrangements of groupings/sections.

FIGS. 4A-4C illustrate example operation of the grouping component 115. Beginning with FIG. 4A, example 400 a symbolically illustrates two sequences of recorded executable instructions for diffing by the debugging component 109, including sequence 401 a on the left for comparison/diffing against sequence 401 b on the right. These sequences 400 can be sequences of executable instructions that executed as part of one or more executable entities (e.g., process(es) or thread(s) executed from application(s) 112), and whose execution is recorded in corresponding replayable execution traces 113 accessed by the trace access component 114 a. For example, sequence 401 a might correspond to one or more first portions of execution of a process of an application 112, while sequence 401 b might correspond to one or more second portions of execution of a process of the same application 112. In this first example, the first portion(s) of execution might correspond to a first time period of execution of an instance of a process/thread, while the second portion(s) of execution might correspond to a second time period of execution of the same instance of the process/thread. Alternatively, the first portion(s) of execution might correspond to execution of a first instance of a process/thread, while the second portion(s) of execution might correspond to execution of a second instance the process/thread (e.g., at the same computer system, or at another computer system). In another example, sequence 401 a might correspond to one or more first portions of execution of a process/thread of one version of an application 112, while sequence 401 b might correspond to one or more second portions of execution of a process/thread of another version of the same application 112. In this second example, the applications 112 could be differently versioned due one or more of code changes, compiler changes, compiler settings changes, processor ISA changes, and the like. As will become clear hereinafter, sequences 400 could represent execution an application 112 using the same input data sets/conditions, or entirely different data sets/conditions.

Turning to FIG. 4B, example 400 b illustrates that grouping component 115 can group each sequence 400 of executable instructions into different groups/sections of related consecutive executable instructions. In the example 400 b, the grouping component 115 initially groups the sequences 400 into sections of executable instructions that executed together as part of a common function. In example 400 b, on sequence 401 a the grouping component 115 has identified sequences of executable instructions that executed as part of functions 402 a, while on sequence 401 b the grouping component 115 has identified sequences of executable instructions that executed as part of functions 402 b. In example 400 b, functions 402 are identified by function name (i.e., a, b, c, etc.) together with function parameters, which are symbolically represented as “( . . . )”. Thus, in example 400 b, the grouping component 115 has leveraged the logical structure of code to identify groupings/sections of consecutive executable instructions that are logically related as having executed together as a common function.

In embodiments, the grouping component 115 can be flexible when identifying sequences of instructions that executed as a common function. For example, the grouping component 115 might define “functions” to correspond to those functions that were defined in an executable entity's source code. This definition might be particularly useful if debugging symbols are available to the debugging component 109, since function names and parameters are typically identifiable within debugging symbols. However, the grouping component 115 could additionally, or alternatively, more flexibly define a “function” to be any sequence of instructions that executed from a defined starting point to a defined ending point. For example, this could be from entry into a source code function to exit from the source code function, between two tracing events (e.g., Event Tracing for Windows, or similar tracing technology), between different function calls (e.g., openwindow( ) to closewindow( ), from thread start to thread exit, etc. When using a more flexible definition of a function, the grouping component 115 might synthesize function names (e.g., using a counter, by instruction count, by stack frame count, etc.) and identify any inputs consumed by the function's sequence of instructions as the function's parameters. A flexible definition of a function can be utilized both when debugging symbols are available, and when they are not. For example, if debugging symbols are not available of an executable entity, the grouping component 115 might define functions as the entity's exported functions.

As mentioned, in embodiments the grouping component 115 identifies hierarchical arrangements of groupings/sections. Turning to FIG. 4C, example 400 c illustrates that grouping component 115 can utilize the hierarchical structure of code to further group the functions 402 illustrated in example 400 c into higher-level groups 403. For example, in example 400 c, functions 402 a are grouped into modules A, B, and K, and functions 402 b are grouped into modules A, B, X and K. More particularly, functions 402 a are grouped into group 403 a-1 comprising a sequence of functions (i.e., a, b, and c) that executed as part of module A, group 403 a-2 comprising a sequence of functions (i.e., a, x, and y) that executed as part of module B, group 403 a-3 comprising a sequence of functions (i.e., a, z, and x) that executed as part of module A, and group 403 a-4 comprising a sequence of functions (i.e., a and b) that executed as part of module K. Similarly, functions 402 b are grouped into group 403 b-1 comprising a sequence of functions (i.e., a, z, and c) that executed as part of module A, group 403 b-2 comprising a sequence of functions (i.e., a, x, and z) that executed as part of module B, group 403 b-3 comprising a sequence of functions (i.e., a, z, and x) that executed as part of module X, and group 403 b-4 comprising a sequence of functions (i.e., a and b) that executed as part of module K. While example 400 c illustrates a two-level hierarchy (i.e., modules and functions), in embodiments the grouping component 115 can create groupings with any number of levels.

FIGS. 4A-4C illustrated two sequences 400 of executable instructions for diffing (i.e., sequence 401 a on the left and sequence 401 b on the right), including example groupings. In these examples, the debugging component 109 would perform a one-to-one (1:1) diffing (i.e., one sequence of instructions on one side against another sequence of instructions on the other side). In embodiments, the debugging component 109 can might perform one-to-many (1:N) diffing (i.e., one sequence of instructions on one side against N sequences of instructions on the other side) and/or many-to-many (M:N) diffing (i.e., M sequences of instructions on one side against N sequences of instructions on the other side). When performing 1:N or M:N diffing, the debugging component 109 might utilize an alignment component 116, as will be discussed later.

Based at least on the groupings identified by the grouping component 115, the diffing component 117 compares one or more first sequence(s) of instructions against one or more second sequence(s) of instructions to identify commonalties and differences among those instructions. In embodiments, rather than comparing exact sequences of instructions, the diffing component 117 compares the logical groupings of instructions identified by the grouping component 115. Thus, in many ways, the diffing component 117 compares how sequences of executable instructions behaved as a group overall, rather than comparing the exact sequence of instructions that were executed (e.g., instruction-by-instruction). As will be explained, this grouping-based diffing greatly reduces the computational complexity of diffing (e.g., as compared to comparing the exact sequence of instructions that were executed, instruction-by-instruction). In addition, as will also be explained, this grouping-based diffing enables the diffing component 117 to offer new and unique capabilities, such as the ability to compare sequences of executable instructions that executed on entirely different processor ISA's (e.g., a sequence of instructions that executed as part of an x86 build of an application 112 versus a sequence of instructions that executed as part of an ARM build of the application 112).

As shown, the diffing component 117 includes a differencing component 117 a which compares different sequences of instructions based on the groupings within those sequences that were identified by the grouping component 115. In embodiments, the differencing component 117 a utilizes a metric, such as an edit distance (e.g., Levenshtein distance), to identify how groups in one sequence of instructions compare to groups in another sequence of instructions. In general, an edit distance is a metric measuring the minimum cost of the single-item edit(s) (e.g., insertions, deletions, or replacements) required to transform one sequence into another sequence. For example, Table 1 and Table 2 below present two examples ways for considering edit distance for the character strings FILES and FRIES, in which the individual items being compared are the individual characters in the strings:

TABLE 1 FILES Edit FRIES F = F I R R L R I E = E S = S

TABLE 2 FILES Edit FRIES F = F + R I = I L − E = E S = S In both tables, the “F”, “E”, and “S” characters can be considered to be equal (=) between the two strings. In Table 1, however, the second and third characters in FILES are considered to be replaced (R) by the second and third characters in FRIES—i.e., the “I” and “L” characters in FILES are replaced with the “R” and “I” characters in FIRES, respectively. In Table 2, on the other hand, the “R” character in FRIES is considered to be an insertion (+), while the “L” character in FILES is considered to be a deletion (−). Thus, in Table 2, the “I” character is considered equal between the two strings.

A decision for whether the edits in Table 1, or the edits in Table 2, are the “minimum” edit distance between the two strings depends on how each edit is weighted. For example, if equal/equivalent characters are given a weight of 0, if additions and deletions are each given a weight of 2, and if replacements are given a weight of 1 (i.e., replacements are preferred over additions and deletions), then the edits of Table 1 would be chosen. This is because the edit distance for Table 1 would be 2, while the edit distance for Table 2 would be 4, and thus Table 1 has the lesser edit distance. If, on the other hand, additions and deletions are instead each given a weight of 1, and replacements are instead given a weight of 2 (i.e., additions and deletions are preferred over replacements), then the edits of Table 2 would be chosen. This is because the edit distance for Table 1 would be 4, while the edit distance for Table 2 would be 2, and thus Table 2 has the lesser edit distance.

In embodiments, the differencing component 117 a applies one or more of the following properties to edit distances:

-   -   1. d(x, x)=0; i.e., the edit distance between equal/equivalent         items is zero.     -   2. d(x, y)=d(y, x); i.e., the edit difference between two items         is the same regardless of the direction of the comparison. For         example, computing an edit difference between FILES and FRIES         would produce the same value as computing an edit difference         between FRIES and FILES.     -   3. d(a, b)+d(b, c)>=d(a, c); i.e., the edit distance between a         first item and a second item, plus the edit distance between the         second item and a third item is equal to, or greater than, the         edit distance between the first and third items.         In some situations, the differencing component 117 a might relax         the second requirement. In these situations, the values computed         by the differencing component 117 a might not be strictly         considered an “edit distance.” However, by relaxing the second         requirement, the differencing component 117 a could, for         instance, consider additions to be more expensive than deletions         (i.e., such that deletions are preferred over additions). When         applying edit distances to code traces, this could mean that         adding a behavior (e.g., a regression) could be considered more         expensive than removing a behavior (e.g., a regression).

As mentioned, the differencing component 117 a can perform diffing based on groups identified by the grouping component 115, rather than diffing instruction streams instruction-by-instruction, which can greatly reduce the computational complexity of the diffing. For instance, if the differencing component 117 a treated each instruction in sequences 401 a and 401 b as individual items for comparison (e.g., much like the individual characters in the examples above), and computed edit distances between these instructions using standard techniques, the algorithm complexity would be O(Y*Z) (using the well-known “Big-O” algorithm complexity notation and the standard implementation of the algorithm), where Y and Z are the number of instructions in each sequence 401 being compared. By limiting a search depth such that only instruction streams that are similar to within a threshold can be successfully compared, this complexity could potentially be improved to O(Y+Z)+d, where d dictates the threshold. Since, as mentioned, modern microprocessors commonly execute at the rate of tens- to hundreds-of thousands of MIPS, traces covering mere seconds of execution time can record the execution of many billions of instructions. As such, diffing on an individual instruction basis can quickly become prohibitively expensive in terms of the computing resources and time required. However, by diffing based on groups, the analysis can instead diff groups of instructions together, eliminating the need to fully compare individual instructions across the traces. In addition, performing diffing based on groups provides opportunities to be intelligently selective as to which the portion(s) of the sequences 401 are actually compared, and at what level of granularity, further reducing the amount of work that may need to be performed. As such, it may be that the techniques herein analyze/compare a mere fraction of the amount of trace data, as compared to an instruction-by-instruction diffing.

In embodiments, the differencing component 117 a performs diffing based on groups by representing those groups in an object notation for which edit distance can be applied. When there is a hierarchy of groups, the differencing component 117 a might perform this differencing at any level of grouping. To demonstrate these concepts FIGS. 5A-5D illustrate example operation of the differencing component 117 a to compare the groups 403 from example 400 c of FIG. 4C. Beginning with FIG. 5A, example 500 a shows example string-based differencing notations for each group 403 from FIG. 4C. In example 500 a, each group 403 is represented as a string comprising a module name, a name of the entry function for the module, and a name of exit function for the module, each separated by an exclamation point (!). Thus, in sequence 401 a, group 403 a-1 is represented by the string “A!a!c”, group 403 a-2 is represented by the string “B!a!y”, group 403 a-3 is represented by the string “A!a!x”, and group 403 a-4 is represented by the string “K!a!b”. In sequence 401 b, group 403 b-1 is represented by the string “A!a!c”, group 403 b-2 is represented by the string “B!a!z”, group 403 b-3 is represented by the string “X!a!x”, and group 403 b-4 is represented by the string “K!a!b”. Notably, the notation used in example 500 a is one example only, and it will be appreciated that a great variety of notations could be used. For example, group 403 a-1 might alternatively be represented as the string “A!a:c”, the string “A:a>c”, the string “A:a:c”, the string “A:a,c”, etc. while capturing the same information.

Based on these group representations, the differencing component 117 a determines, as between sequences 401 a and 401 b, whether a group 403 in one sequence 401 is equal to a corresponding group 403 in the other sequence 401, whether a group 403 is inserted/added in one sequence 401 as compared to the other sequence 401, whether a group 403 is deleted/subtracted in one sequence 401 as compared to the other sequence 401, or whether a group 403 in one sequence 401 is a replacement of a corresponding group 403 in the other sequence 401. In this context, “equal” groups can include not only groups that executed exactly the same (i.e., the sequence of instructions in each group are identical), but also groups that executed equivalently—even if the precise sequences of instructions executed in each group differ. Thus, two groups of instructions can be considered “equal” (or “equivalent”) even if those instructions were from different processor ISAs, were from different builds/versions of an application, etc.

Turning to FIG. 5B, example 500 b illustrates example group comparison status based on these differencing notations. In particular, example 500 b shows that the differencing component 117 a might determine that—at least when differencing at the level of groups 403—group 403 a-1 on sequence 401 a is equal (equivalent) to group 403 b-1 on sequence 401 b, group 403 a-2 on sequence 401 a is replaced by group 403 b-2 on sequence 401 b, group 403 a-3 on sequence 401 a is replaced by group 403 b-3 on sequence 401 b, and group 403 a-3 on sequence 401 a is equal (equivalent) to group 403 b-4 on sequence 401 b. In this example, the differencing component 117 a might have weighted replacements as being preferred over insertions and deletions. Since the differencing component 117 a has compared a notational representation of the groups, rather than the sequences of individual instructions in the groups, this comparison can take a fraction of the computing resources than would be needed to compare the sequences of individual instructions.

As will be recognized by one of ordinary skill in the art, the foregoing determination of equality/equivalency (e.g., between groups 403 a-1 and 403 b-1 and groups 401 a-4 and 403 b-4) only indicates that each set of groups began by executing the same module and function (i.e., A!a) and ended by executing the same module and function (i.e., A!c). While this may be an imprecise indication of equality/equivalency (e.g., group 403 a-1 also executed function b, while group 403 b-1 instead executed function z), due to the structured nature of program code an indication of this level of equality/equivalency may be sufficient to provide a behavioral overview of how one trace of an application 112 compares to another trace of the application 112. For instance, even though groups 403 a-1 and 403 b-1 may have diverged somewhat internally, they started with the same function (i.e., A!a) and ended with the same function (i.e., A!c). When presenting an overview of program execution flow, particularly as higher levels of granularity such as at a module level, this may be sufficient to convey behavioral similarities and differences. For example, if module A is a memory allocation library, in both instances the module may have been called (e.g., using an exported function, a) with a request for a particular amount of memory, and may have exited (e.g., using an internal function, c) with an indication of success and/or with a pointer. Thus, the overall behavior of the module was similar in both traces, even if the particular work performed internally by the module diverged.

In embodiments, the differencing component 117 a might also consider data, such as a group's inputs and outputs, when comparing equality/equivalency for two groups. For example, returning to the example of groups 403 a-1 and 403 b-1, in addition to comparing the group object notations (e.g., the string “A!a!c” for each group), the differencing component 117 a might also identify and compare the inputs (if any) and the outputs of the group. For example, the differencing component 117 a could identify input memory values read (if any) by the instructions in groups 403 a-1 and 403 b-1, as well as output memory values written by the instructions in groups 403 a-1 and 403 b-1. Then, the differencing component 117 a can compare these values across the sequences 401. If groups 403 a-1 and 403 b-1 both read the same input values, and if groups 403 a-1 and 403 b-1 both wrote the same output values, the differencing component 117 a might have a high confidence in a determination of equality/equivalency between these groups based on comparing object notations (e.g., the string “A!a!c” for each group). Note that this may be true even though these groups executed different intermediary functions (e.g., function b in group 403 a-1 b versus function z in group 403 b-1). This is because groups 403 a-1 and 403 a-1 both produced the same outputs when given the same inputs, even though the processing utilized by those groups to arrive at those outputs might have diverged.

As mentioned, when there is a hierarchy of groups, the differencing component 117 a might perform differencing at any level of grouping. Thus, for example, the comparison status shown in FIG. 5B might be an initial comparison status resulting from a first pass by the differencing component 117 a. Based on this initial comparison status, the differencing component 117 a might make one or more additional passes using groupings lower in the hierarchy. For example, the differencing component 117 a might further compare the sub-groupings within groups 403 a-1 and 403 b-1 to determine if an initial determination of equality/equivalency was accurate or not. Thus, for instance, the differencing component 117 a might compare the individual sequences of functions within those groups. To illustrate, the differencing component 117 a might determine that, within groups 403 a-1 and 403 b-1, function A!a on sequence 401 a is equal to function A!a on sequence 401 b, function A!b on sequence 401 a is replaced by function A!z on sequence 401 b, and function A!c on sequence 401 a is equal to function A!c on sequence 401 b. Since, in this second pass, the differencing component 117 a determined that function A!b on sequence 401 a was replaced by function A!z on sequence 401 b, the differencing component 117 a might update the comparison status of groups 403 a-1 and 403 b-1 to be a replacement, instead of equality/equivalency. Performance of this additional pass for groups 403 a-1 and 403 b-1 could be triggered in a variety of manners. For example, the differencing component 117 a might perform an additional pass on any groups that were initially determined to be equal, in order to verify that status. In another example, the differencing component 117 a might perform an additional pass on only groups that are specifically requested by a user.

The examples shown in FIGS. 5A and 5B are only one way in which the differencing component 117 a might go about performing a comparison. For example, rather than initially using only the beginning and ending functions in a group as part of the comparison, the differencing component 117 a might have used all functions in each group. Thus, for example, the differencing component 117 a might have compared the string “A!a!b!c” for group 503 a-1 with the string “A!a!z!c” for group 503 a-1, might have compared the string “B!a!x!y” for group 503 a-2 with the string “B!a!x!z” for group 503 a-2, and so on. Additionally, the examples in FIGS. 5A and 5B demonstrated a hierarchy having two levels of groupings of instructions (i.e., modules->functions). However, the grouping component 115 might have instead identified a hierarchy having one or more additional levels of groupings (e.g., modules->classes->functions), and the differencing component 117 a might include these additional level(s) as part of its analysis. For instance, the differencing component 117 a might make a first pass at a module level, might make a second pass at a class level (for at least a subset of modules), and make a third pass at a function level (for at least a subset of classes). Furthermore, the examples in FIGS. 5A and 5B used only function names as part of the comparison. In embodiments, the differencing component 117 a might further include function parameter information as part of the comparison (e.g., parameter name, parameter type, parameter count, etc.). For instance, the notation for representing group 503 a-1 might be the string “A!a[height,width]!b[status]” (i.e., using parameter names), the string “A!a[int,int]!b[bool]” (i.e., using parameter types), the string “A!a[2]!b[1]” (i.e., using parameter counts), and the like.

In embodiments, the differencing component 117 a applies weightings to different classifications types while making edit distance determinations. For example, the differencing component 117 a might weight insertions and deletions differently than replacements, and might even weight insertions differently than deletions. In embodiments, the differencing component 117 a might also apply different weights to different components of a group's identification object. For example, when representing groups using strings of the form module!entry!exit, the differencing component 117 a could compare individual components of those strings (e.g., module to module, entry function to entry function, and exit function to exit function), and apply different weightings to those components. For instance, the differencing component 117 a might assign a greater weight to modules than it does to functions. Then, for example, if the modules for two groups are the same, but there are differences in the functions, this weighting might be used to determine if an edit should be classified as a replacement, or as an insertion/deletion. This weighting could even be applied more granularly, such as to parameter information (e.g., name, type, count, etc.).

In embodiments, the differencing component 117 a intelligently adapts to identified differences between the comparison data sets. For example, the diffing component 117 is shown as including a transformation component 117 b. In embodiments, the transformation component 117 b interoperates with the differencing component 117 a to apply one or more transformations based on known changes to at least one instruction sequence prior to computing differences. For example, suppose that, in an updated build of an application, a module, class, function, etc. as globally renamed. While, if performed properly, such a global rename should not affect the execution behavior of the application, this rename could result in the differencing component 117 a identifying differences which really do not matter from a behavioral standpoint. Thus, the transformation component 117 b can apply transformations in order to avoid such “false” differences. Referring to FIG. 5B, for example, group 403 a-3 and 403 b-3 are shown as having a replacement status. As will be appreciated, this is because the differencing component 117 a compared A!a!x against X!a!x. However, if it was known that, in a build of the traced application 112 that was used to generate sequence 401 b, module A was renamed to module X, the transformation component 117 b might transform the notation for group 403 b-3 from X!a!x to A!a!x prior to the differencing component 117 a making a comparison. Thus, when performing its analysis after the transformation, the differencing component 117 a would classify these groups as being equal, instead of replacements. In this way, the transformation component 117 b can help reduce “noise” and focus the identified differences on those that may actually matter from a behavioral standpoint.

In addition to comparing groups based on group identity and edit distance, as has been described, the differencing component 117 a can also utilize an emulation comparison component 117 c to determine whether or not the sequences of instructions in different functions actually executed equivalently. In embodiments, different sequences of instructions execute equivalently if both sequences of instructions produce the same outputs when given the same inputs. Thus, as part of comparing functions, the emulation comparison component 117 c can identify zero or more inputs to each comparison function, and zero or more outputs from the comparison functions. Then, based on supplying the inputs of each comparison function with the code of the other comparison function, the emulation comparison component 117 c can emulate that code with the emulation component 111 to determine if there is a code equivalency. In embodiments, the emulation comparison component 117 c utilizes one or more of the techniques described in Applicant's co-pending application, U.S. patent application Ser. No. 16/358,221, filed Mar. 19, 2019, and titled “EMULATING NON-TRACED CODE WITH A RECORDED EXECUTION OF TRACED CODE,” the entire contents of which are incorporated by reference herein in their entirety.

FIGS. 5C and 5D demonstrate operation of the emulation comparison component 117 c, based on utilizing code emulation and inputs/outputs comparison to determine if functions on different traced instruction sequences executed equivalently. Referring to FIG. 5C, example 500 c shows that, on sequence 401 a, the code 405 a of function A!b from group 403 a-1 has inputs 404 a and outputs 406 a. In addition, example 500 c shows that, on sequence 401 b, the code 405 b of function A!z from group 403 b-1 has inputs 404 b and outputs 406 b. In order to compare equivalency of code 405 a and 405 b, the example 500 d in FIG. 5D demonstrates that the emulation comparison component 117 c can emulate code 405 b (i.e., from sequence 401 b) using inputs 404 a (i.e., from sequence 401 a), which will result in some output 407. Example 500 d also demonstrates that the emulation comparison component 117 c can also emulate code 405 a (i.e., from sequence 401 a) using inputs 404 b (i.e., from sequence 401 b), which will result in some output 408. The emulation comparison component 117 c can then determine whether outputs 407 and 408 indicate an equivalency between code 405 a and 405 b. For example, if output 407 is the same as output 406 a, and if output 408 is the same as output 406 b, then code 405 a and 405 b execute equivalently. In this situation, the differencing component 117 a might determine that function A!b in group 403 a-1 and function A!z in group 403 a-2 are equivalent to each other (e.g., rather than replacements or insertions/deletions). If output 407 is the not the same as output 406 a and/or output 408 is not the same as output 406 b, then the code 405 a and 405 b do not execute equivalently. In this situation, the differencing component 117 a might determine that function A!b in group 403 a-1 and function A!z in group 403 a-2 are not equivalent to each other (e.g., and, thus, are replacements or insertions/deletions).

Notably, the emulation comparison component 117 c can determine whether or not different code from different sequences to be equivalent even those sequences were executed on different processor ISA's and/or if those sequences were executed from different builds/versions of an application 112. This is because the emulation comparison component 117 c identifies equivalency based on comparing the behavior of sequences of instructions (i.e., how they transformed input data to produce output data), rather than based on comparing the actual instructions executed.

Using the techniques discussed, the emulation comparison component 117 c can determine whether or not different portions of code executed equivalently, even if the inputs to that code were not the same. For instance, the emulation comparison component 117 c can determine whether or not code 405 a and 405 b execute equivalently, even if inputs 404 a are different than inputs 404 b. If inputs are different, then the debugging component 109 might determine why the inputs are different. For example, the debugging component 109 could process each trace backwards to determine where the values of the inputs originated (i.e., where they were written to a memory location used as an input).

The diffing component 117 is also shown as including a transitive analysis component 117 d and a ranking/correlation component 117 e. In embodiments, these components are utilized when performing 1:N or M:N diffing, and will be discussed later.

The output component 118 can provide one or more indicia of a result of the comparing by the diffing component 117. This can include providing one or more indicia to a software component at computer system 101, or to another computer system (e.g., using network device(s) 105). The indicia can indicate a comparison status determined by the diffing component 117 for one or more groups identified by the grouping component 115. In embodiments, based on an indicia produced by the output component 118, a software component presents a result of the comparing by the diffing component 117 at a user interface. For example, a user interface might provide a side-by-side visual representation of groups on each of sequences 401, indicating where those groups are equal, inserted, deleted, etc. For instance, Table 3 illustrates that the groups in FIG. 5B might be presented side-by-side by aligning equal groups and indicating which groups are replacements. In Table 3, replacements are indicated using parenthesis, though a user interface could provide such indications in a great variety of manners (e.g., colors, shading, bolding, etc.).

TABLE 3 A!a!c A!a!c (B!a!y) (B!a!z) (A!a!x) (X!a!x) K!a!b K!a!b In embodiments, a user interface might visually apply shifts, as appropriate. For example, suppose that group 403 b-3 (i.e., X!a!x) did not exist in any of the illustrated examples. In this instance, the combination of groups 403 a-2 (i.e., B!a!y) and 403 a-3 (i.e., A!a!x) might together be considered a replacement for group 403 b-2 (i.e., B!a!z). Table 4 illustrates that, in this instance, a user interface might visually shift group 403 b-4 (i.e., K!a!b) the right side of the presentation down to adapt to this replacement.

TABLE 4 A!a!c A!a!c (B!a!y) (B!a!z) (A!a!x) K!a!b K!a!b By applying visual shifts in this way, a user interface can enable a user to quickly identify areas in which two sequences 401 executed similarly, and areas in which two sequences 401 they executed differently. In embodiments, to provide a more condensed view, a user interface might provide a capability to visually expand and collapse sections of inequality.

In view of the foregoing discussion of performing a 1:1 execution trace diffing (i.e., one sequence of instructions on one side against another sequence of instructions on the other side) using the debugging component 109, FIG. 6 illustrates a flowchart of an example method 600 for diffing a subject replayable execution trace against a comparison replayable execution trace. Method 600 will now be described within the context of with FIGS. 1-5D. While, for ease in description, the acts of method 600 are shown in a particular sequential order, it will be appreciated that some of these acts might be implemented in different orders, and/or in parallel.

As shown in FIG. 6, method 600 includes an act 601 of accessing a subject trace and a comparison trace. In some embodiments, act 601 comprises accessing a first subject replayable execution trace which represents a first sequence of executable instructions that executed as part of a first executing entity, and accessing a second comparison replayable execution trace which represents a second sequence of executable instructions that executed as part of a second executing entity. For example, the trace access component 114 a can access two or more execution traces 113, or two different portions of the same execution trace 113, which record one or more prior executions of an application 112. If there are multiple execution traces 113, the first executing entity and the second executing entity might have executed from common executable code (e.g., the same version of application 112), or from different executable code (e.g., different versions or different builds of application 112). In embodiments, the accessed execution trace(s) 113 represent sequences of executable instructions that were previously executed, and/or can represent sequences of executable instructions that could be executed (i.e., a synthetic trace). Thus, use of the past-tense term “executed” herein can also refer to sequences of instructions that could be executed, even if they did not actually execute previously. For example, FIG. 4A illustrates two sequences of executable instructions—i.e., sequence 401 a and sequence 401 b. Sequences 401 a and 401 b might correspond to the accessed first sequence of executable instructions and second sequence of executable instructions, respectively.

Method 600 also includes an act 602 of identifying functions within the subject and comparison traces. In some embodiments, act 602 comprises identifying a first plurality of functions within the first sequence of executable instructions, and identifying a second plurality of functions within the second sequence of executable instructions, each function corresponding to a sequence of one or more executable instructions that executed as part of the function. For example, for each of sequences 401 a and 401 b, the grouping component 115 can identify groups or sections of consecutive instructions that executed together as a common function. For instance, FIG. 4B illustrates that the grouping component 115 might identify a first plurality of functions 402 a on sequence 401 a, and second plurality of functions 402 a on sequence 401 b. In FIG. 4A, these functions 402 are shown as having function names (e.g., a, b, c, etc.) and possibly some function parameters (e.g., indicated as “( . . . )”). As such, as part of act 602, identifying the first plurality of functions and identifying the second plurality of functions might comprise identifying, for each function of the first plurality and second plurality of functions, at least one of a function name, a function parameter name, a function parameter type, or a function parameter count.

Method 600 also includes an act 603 of identifying groupings of the functions within the subject and comparison traces. In some embodiments, act 603 comprises identifying a first plurality of groups of the first plurality of functions, and identifying a second plurality of groups of the second plurality of functions, each group comprising a sequence of one or more related functions. For example, as demonstrated in FIG. 4C, the grouping component 115 could identify groups of functions that are logically related, such as being functions that executed together as a common module. For instance, FIG. 4C illustrates a first plurality of groups 403 a-1 through 403 a-4 on sequence 401 a, and a second plurality of groups 403 b-1 through 403 b-4 on sequence 401 b. While example 400 c of FIG. 4C provided groupings based on modules, these groupings could be based on any logical code structure. For example, in act 603, each group might correspond to one of a library, a module, a namespace, or a class; in this case, each related function would have executed as part of the corresponding library, module, namespace, or class. As discussed, the grouping component 115 could identify a hierarchy comprising any number of groups. For instance, if the first and second pluralities of groups corresponded to modules (as in FIG. 4C), then a higher-level group might correspond to libraries, in which each higher-level group comprises a sequence of one or more modules that executed together as part of a common library.

Method 600 also includes an act 604 of comparing the groupings to identify groups in the subject trace that equal, replace, are inserted into, and/or are deleted from groups in the comparison traces. In some embodiments, act 604 comprises comparing the first plurality of groups and the second plurality of groups, including determining, based on an identity of each group and on one or more functions corresponding to the group, if each first group in the first plurality of groups is at least one of equal to a second group in the second plurality of groups; a replacement of a second group in the second plurality of groups; deleted from the second plurality of groups; or inserted into the second plurality of groups. For example, the diffing component 117 can utilize the differencing component 117 a to compare groups in the first plurality of groups to groups in the second plurality of groups to classify each first group as having an equal in the second groups, as being a replacement of a second group in the second plurality of groups, as being inserted into the first plurality of groups as compared to the second plurality of groups, or as being deleted from the first plurality of groups as compared to the second plurality of groups. The differencing component 117 a could also do a comparison the other way—i.e., by comparing groups in the second plurality of groups to groups in the first plurality of groups to classify each second group as having an equal in the first groups, as being a replacement of a first group in the first plurality of groups, as being inserted into the second plurality of groups as compared to the first plurality of groups, or as being deleted from the second plurality of groups as compared to the first plurality of groups. In embodiments the differencing component 117 a computes an “edit distance” for each group, and chooses a combination of single-group edits that produce a minimum overall edit distance between the two pluralities of groups.

In embodiments, comparing the first plurality of groups and the second plurality of groups comprises creating a first plurality of objects each representing one of the first plurality of groups, and creating a second plurality of objects each representing one of the second plurality of groups, each objects identifying the group and one or more corresponding functions of the group, and applying a differencing algorithm between the first plurality of objects and the second plurality of objects. An object could take wide variety of forms, such as a hierarchical structure, a string, etc. In embodiments, an object might separately represent modules, functions, etc., in a manner that enables these individual components to be compared across two different object (e.g., module in object A to module in object B, function in object A to function in object B, etc.), and that enables the individual components to be weighted separately. For simplicity, the examples herein present objects in the form of strings. For example, as demonstrated in FIG. 5A, the differencing component 117 a might represent groups by module name and the names of one or more functions that executed as part of the module (e.g., the string A!a!c for group 503 a-1, the string B!a!y for group 503 a-2, etc.). In this example, each object identifies a group and a plurality of corresponding functions of the group, in which the plurality of corresponding functions ordered in an execution order. Additionally, in this example, each plurality of corresponding functions includes only a first function and a last function that executed in the execution order. Comparing the first plurality of groups and the second plurality of groups might further comprise comparing at least one of a function parameter name, a function parameter type, or a function parameter count. Thus, these objects might also incorporate parameter information. Additionally, when comparing the first plurality of groups and the second plurality of groups, the comparison might weight an identity of each group differently than an identity of at least one function corresponding to the group.

As mentioned, the diffing component 117 might also utilize the transformation component 117 b to apply one or more transformations based on known changes to at least one of the comparison instruction sequences prior to computing differences with the differencing component 117 a. For instance, if there was a global rename in a version of application 112 used to generate sequence 401 b as compared to a version of application 112 used to generate sequence 401 a, the transformation component 117 b might apply transformations to sequence 401 b, or data generated therefrom, prior to doing a comparison with the differencing component 117 a. Thus, act 604 might include, when comparing the first plurality of groups and the second plurality of groups, applying one or more transformations to at least a subset of at least one of the first replayable execution trace or the second replayable execution trace.

As was also mentioned the diffing component 117 might also utilize the emulation comparison 117 c to determine whether the actual instructions in functions on different traces executed equivalently. Thus, act 604 might include determining whether a first function corresponding to a first group of the first plurality of groups executes equivalently to a second function corresponding to a second group of the second plurality of groups. As discussed, the emulation comparison 117 c might accomplish such a determination based on using inputs for a function in one sequence of instructions to emulate code from a function in another sequence of instructions, and vice versa, and analyzing the generated outputs. Thus, determining whether the first function (e.g., A!b in group 401 a-1) executes equivalently to the second function (e.g., A!z in group 403 b-1) might include identifying zero or more first inputs (e.g., inputs 404 a) to the first function (e.g., code 405 a) and one or more first outputs (e.g., outputs 406 a) from the first function, and identifying zero or more second inputs (e.g., inputs 404 b) to the second function (e.g., code 405 b) and one or more second outputs from the second function (e.g., outputs 406 b). The determining might also include replaying the second function (e.g., code 405 b) based on supplying the second function with the zero or more first inputs (e.g., inputs 404 a) to generate one or more third outputs (e.g., outputs 407), and replaying the first function (e.g., code 405 a) based on supplying the first function with the zero or more second inputs (e.g., inputs 404 b) to generate one or more fourth outputs (e.g., outputs 408). The determining might also include comparing the first outputs (e.g., outputs 406 a) with the third outputs (e.g., outputs 407), and comparing the second outputs (e.g., outputs 406 b) with the fourth outputs (e.g., outputs 407).

Method 600 also includes an act 605 of providing an indicia of a result of the comparing. In some embodiments, act 605 comprises providing one or more indicia of a result of the comparing to a software component at the computer system, or to another computer system, the one or more indicia indicating whether each first group is at least one of equal to a second group in the second plurality of groups, a replacement of a second group in the second plurality of groups, deleted from the second plurality of groups, or inserted into the second plurality of groups. For example, the output component 118 can provide an indicia of any of the differencing information produced by the diffing component 117 to a component at computer system 101, or to another computer system (e.g., using network device(s) 105). In embodiments, providing the one or more indicia of the result of the determining causes a software component to present the result of the determining at a user interface. For example, as demonstrated in tables 3 and 4, a user interface might provide a side-by-side visual comparison of two sequences of instructions, based on the groups identified by the grouping component 115 and as compared by the diffing component 117. As mentioned, this could include providing a capability to visually expand and collapse sections of inequality. Thus, presenting the result of the comparing might comprise visually collapsing a sequence of the first plurality of groups that are not equal to second groups in the second plurality of groups.

While the debugging component 109 has been described thus far primarily in the context of performing a 1:1 diffing (i.e., one sequence of instructions on one side of a comparison against another sequence of instructions on the other side of the comparison), as indicated the debugging component 109 can in embodiments perform 1:N diffing (i.e., one sequence of instructions on one side against N sequences of instructions on the other side) and/or M:N diffing (i.e., M sequences of instructions on one side against N sequences of instructions on the other side). For example, in a 1:N diffing situation, the debugging component 109 might diff a single trace captured using a testing build of an application 112 against multiple traces captured using a production build of the application 112, or might diff a single trace captured within a testing environment against multiple traces captured within a production environment. To illustrate, FIG. 7A shows an example 700 a of 1:N trace comparison, in which there is a single sequence of instructions on the left side of the comparison, and two or more different sequences of instructions on the right side of the comparison. In a M:N situation, the debugging component 109 might diff multiple traces captured using a testing build of an application 112 against multiple traces captured using a production build of the application 112, or might diff multiple traces captured within a testing environment against multiple traces captured within a production environment. FIG. 7C shows an example 700 c of M:N trace comparison, in which there are multiple sequences of instructions both sides of the comparison.

When multiple traces are involved on at least one side the comparison, the debugging component 109 might utilize the alignment component 116 prior to performing a comparison by the diffing component 117. The alignment component 116 enables use of partial traces on one or more sides of the comparison. FIG. 7A showed two full traces on the right, and FIG. 7C showed two full traces on both the left and the right. In these instances, each execution trace 113 records comparable execution coverage. For example, each execution trace 113 might each record the full execution of an application 112 from beginning to end, in which case the debugging component 109 can compare that full execution. In another example, each execution trace 113 might each record the full execution of a particular sub-component an application 112 from beginning to end in which case the debugging component 109 can compare full execution of that sub-component. However, there may be cases in which execution traces 113 records different pieces an application's execution, such as between thread transitions, between transitions from user mode to kernel mode, for only particular modules or functions, for only times when there were sufficient computing resources at the tracing computer system to allow for trace recording, etc.

The alignment component 116 can align two or more partial traces based on commonalities among those traces (e.g., comparable sequences of groupings) to provide a more complete trace coverage than is provided by each of those partial traces individually. For example, FIG. 7B shows an example 700 b of 1:N trace comparison, in which the right side of the comparison is made up of multiple partial traces that have been aligned by the alignment component 116 so that a complete comparison can be made with the sequence of instructions on the left side of the comparison. FIG. 7D shows an example 700 d of M:N trace comparison, in which partial traces are used on both sides of the comparison. Notably, partial traces can be used in combination with full traces on a given side of the comparison. For example, in FIG. 7D, the right side of the comparison utilizes one full trace and two partial traces.

The alignment component 116 is shown as including an exact match component 116 a and an approximate match component 116 b. These components 116 a, 116 b demonstrate that the alignment component 116 can utilize a variety of techniques to determine how two or more traces align. For example, using the exact match component 116 a, the alignment component 116 might utilize a shortest common supersequence algorithm, which takes two sequences as inputs, and which finds a shortest possible common supersequence of those input sequences. Using the approximate match component 116 b, on the other hand, the alignment component 116 might utilize an algorithm that allows for gaps when matching inputs sequences, such as the Needleman-Wunsch algorithm. Regardless of the type of matching used, the alignment component 116 might perform its matching based on groups of instructions identified by the grouping component 115 (e.g., functions, modules, etc.), rather than based on matching individual instructions.

As mentioned, the diffing component 117 may include a transitive analysis component 117 d and a ranking/correlation component 117 e, which are utilized when performing 1:N and M:N diffing. In embodiments, the transitive analysis component 117 d utilizes the transitive property of equality (i.e., if A=B and B=C, then A=C) to reduce the amount of processing performed by the diffing component 117, by reducing duplicative analysis by the differencing component 117. In particular, for a given set of two or more traces, the transitive analysis component 117 d identifies which sections two or more traces are equivalent, so that the analysis by the transitive analysis component 117 d on one of the traces in the set can be applied to the other trace(s) in the set. In this way, the differencing component 117 can focus on analyzing distinct sections of the traces, rather than analyzing duplicative sections across the traces. To illustrate, suppose that on one side of the comparison there are four traces that execute three sections of instructions (e.g., functions) as shown in Table 5:

TABLE 5 T1 T2 T3 T4 1: A A A A 2: B D X B 3: C C C C In table 5, sections with the same label (e.g., A, B, C, etc.) execute equivalently. Thus, at position 1, section A on trace T1 is equivalent to section A on trace T2, section A on trace T2 is equivalent to section A on trace T3, and section A on trace T4 is equivalent to section A on trace T4. By the transitive property of equality, section A on trace T1 is also equivalent to section A on trace T3 and section A on trace T4, section A on trace T2 is also equivalent to section A on trace T4, etc. At position 3, the same is true for section C as it relates across traces T1, T2, T3, and T4. At position 2, the only equality is between section B on trace T1 and section B on trace T4.

This equality can be viewed as set of mappings, in which each mapping identifies corresponding sections that execute equivalently across multiple traces. A first mapping might map section A at position 1 to traces T1, T2, T3, and T4, a second mapping might map section B at position 2 to traces T1 and T4, and a third mapping might map section C at position 3 to traces T1, T2, T3, and T4. Based on these mappings, distinct sections can be identified. For example, a set of distinct sections across traces T1, T2, T3, and T4 might be: section A on trace T1, section B on trace T1, section D on trace T2, section X on trace T3, and section C on trace T1. Thus, in embodiments, the differencing component 117 might focus its analysis on these distinct sections, and use the transitive property to apply that analysis across the traces.

When performing 1:N diffing, the ranking/correlation component 117 e can rank identified differences between the subject execution trace and the plurality of comparison execution traces, based on how frequently those differences occur between the subject execution trace and the plurality of comparison execution traces. Based on these rankings, the ranking/correlation component 117 e can help identify which differences might be considered to be more important than others. For example, if a first section/group in a subject execution trace is found to be different than all corresponding sections/groups the plurality of comparison execution traces, and if a second section/group in a subject execution trace is found to be different than less than all corresponding sections/groups the plurality of corresponding traces, then a first difference between the first section/group and the comparison execution traces might be ranked more highly than a second difference between the second section/group and the comparison execution traces. Thus, the first difference might be considered to be more important than the second difference.

When performing M:N diffing, the ranking/correlation component 117 e can determine which differences between a group of subject sections (selected across the plurality of subject execution traces) and a group of comparison sections (selected across the plurality of comparison execution traces) correlate highly with a particular section belonging to a group. As used herein, a “comparison section” is any subset of a trace that it big enough to contain one or more diffable events. For example, a comparison section might be a function or a group of functions (e.g., module, class, etc.). To illustrate, if a comparison section is from a function call to its return, then any piece of code that contains a function call or a function return is a diffable section. This can be true even if grouping by module first. Notably, a given event may belong to multiple comparison sections. For example, referring to Table 5, a comparison section could comprise the instructions in A plus the instructions in B, or a comparison section could comprise the second half of the instructions in A plus the first half of the instructions in B. If gaps are allowed, a comparison section could even comprise the first half of the instructions in A plus the second half of the instructions in B.

FIG. 8 illustrates a flowchart of an example method 800 for diffing a subject replayable execution trace against a plurality of comparison replayable execution traces (i.e., a 1:N diffing). Method 800 will now be described within the context of with FIGS. 1A-7D. While, for ease in description, the acts of method 800 are shown in a particular sequential order, it will be appreciated that some of these acts might be implemented in different orders, and/or in parallel.

As shown in FIG. 8, method 800 includes an act 801 of accessing a subject trace and a plurality of comparison traces. In some embodiments, act 801 comprises accessing a subject replayable execution trace, and accessing a plurality of comparison replayable execution traces, each replayable execution trace representing a corresponding sequence of executable instructions that executed as part of a corresponding executing entity. For example, similar to act 601 of method 600, act 801 can utilize the trace access component 114 a to access execution traces 113. However, in act 801, the trace access component 114 a can access an execution trace 113 as a subject execution trace, and access two or more execution traces 113 as comparison execution traces. For instance, referring to FIGS. 7A and 7B, the trace access component 114 a might access one execution trace 113 for the left side of the comparison, and access two or more execution traces 113 for the right side of the comparison.

As mentioned, the debugging component 109 might utilize the alignment component 116 to align partial traces, such as is shown in the right side of the comparison in FIG. 7B. Thus, in act 801, at least one of the plurality of comparison replayable execution traces may be a partial trace, and method 800 might include aligning the partial trace with at least one other of the plurality of comparison replayable execution traces using the alignment component 116. In embodiments, aligning the partial trace with the at least one other of the plurality of comparison replayable execution traces comprises applying at least one of a shortest common supersequence alignment algorithm (e.g., exact match component 116 a) or an approximate string alignment algorithm (e.g., approximate match component 116 b).

Method 800 also includes an act 802 of identifying mappings of sections among the comparison traces that execute equivalently. In some embodiments, act 802 comprises identifying a set of mappings among the plurality of comparison replayable execution traces, each mapping of the set of mappings identifying two or more corresponding comparison sections of consecutive executable instructions within the plurality of comparison replayable execution traces that execute equivalently, each comparison section in each mapping being from a different one of the plurality of comparison replayable execution traces. For example, the transitive analysis component 117 d can analyze the plurality of comparison replayable execution traces to identify corresponding sections across these replayable execution traces that execute equivalently. Referring to Table 5, for example, if the plurality of comparison execution traces included traces T1-T4, the transitive analysis component 117 d might identify a first set of mappings at position 1 (i.e., section A on traces T1-T4), a second set of mappings at position 2 (i.e., section B on traces T1 and T4), and identify a first set of mappings at position 3 (i.e., section C on traces T1-T4).

Method 800 also includes an act 803 of, based on the mappings, identifying distinct sections in the comparison traces. In some embodiments, act 803 comprises, based on the set of mappings, identifying a plurality of distinct comparison sections within the plurality of comparison replayable execution traces, each distinct comparison section either (i) lacking a mapping in the set of mappings, or (ii) being a representative comparison section from a different mapping in the set of mappings. For example, based on the mappings identified in act 802, the transitive analysis component 117 d can identify distinct sections within the plurality of comparison execution traces to compare against sections in the subject execution trace. For instance, referring again to Table 5, the transitive analysis component 117 d could (i) identify sections D (trace T2) and X (trace T3) as sections that lack a mapping in the set of mappings, and (ii) identify sections A, B, and C on trace T1 as sections that are representative comparison sections from different mappings in the set of mappings. Notably, with respect to representative sections A, B, and C, the transitive analysis component 117 d might have alternatively chosen those sections from among the other traces.

Notably, in act 803, the transitive analysis component 117 d might choose less than all possible distinct comparison sections. For instance, the transitive analysis component 117 d might initially choose to focus on sections that occur on more than one trace. In this case, the transitive analysis component 117 d might (at least in a first pass) select only representative comparison sections from the set of mappings and skip sections that lack a mapping in the set of mappings. Thus, in act 803, the plurality of distinct comparison sections might comprise less than all distinct comparison sections within the plurality of comparison replayable execution traces.

Method 800 also includes an act 804 of comparing sections in subject trace with the distinct sections in the comparison traces. In some embodiments, act 804 comprises comparing the subject replayable execution trace and the plurality of comparison replayable execution traces, including at least comparing each of a plurality of subject sections of consecutive executable instructions within the subject execution trace against one or more of the plurality of distinct comparison sections. For example, similar to act 604 of method 600, act 804 can utilize the differencing component 117 a to compare subject sections in the subject execution trace to comparison sections in the comparison execution traces. However, rather than comparing the subject sections to comparison sections in each comparison execution trace, the differencing component 117 a can compare them to only those comparison sections that were identified by the transitive analysis component 117 d as distinct sections.

Method 800 also includes an act 805 of, using the transitive property, determining a comparison status for each section of the subject trace with the comparison sections in the comparison traces. In some embodiments, act 805 comprises, based on the comparing, determining a comparison status of each of the plurality of subject sections, including determining at least one of whether each subject section is (i) equal to at least one corresponding distinct comparison section, or (ii) different than the plurality of distinct comparison sections, wherein the determined comparison status of at least one particular subject section with respect at least one particular corresponding distinct comparison section is applied to each additional comparison section to which the at least one particular distinct comparison section is mapped in the set of mappings. For example, as a result of act 804, the differencing component 117 a can determine a comparison status of each subject section as it relates to a corresponding distinct comparison section. For instance, the differencing component 117 a can determine that a subject section is equal to, or different than, a corresponding distinct comparison section. Then, based on the transitive property, the transitive analysis component 117 d can apply this comparison status to other corresponding comparison sections in the comparison execution traces. Referring to Table 5, for example, suppose that the differencing component 117 a determined that a first subject section is equal to section A in trace T1, that a second subject section is different than section B in trace T1, and that a third subject section is equal to section C in trace T1. Using the transitive property, the transitive analysis component 117 d can apply this status to traces T2, T3, and T4. For instance, the transitive analysis component 117 d can determine that the first subject section also equal to section A in traces T2-T4, that the second subject section is also different than section B in trace T4, and that the third subject section is also equal to section C in traces T2, T3, and T4.

In act 805, a subject section might be different than a comparison section because it is a replacement, an insertion, or a deletion. Thus, in act 805, determining that a subject section is different than the plurality of distinct comparison sections can comprise determining that the subject section is at least one of a replacement of one of the plurality of distinct comparison sections, deleted from the plurality of distinct comparison sections, or inserted into the plurality of distinct comparison sections.

Method 800 also includes an act 806 of providing an indicia of a result of the determining. In some embodiments, act 806 comprises providing an indicia of a result of the determining to a software component at the computer system, or to another computer system. For example, similar to act 605 of method 600, in act 806 the output component 118 can provide an indicia of any of the differencing information produced by the diffing component 117 to a component at computer system 101, or to another computer system (e.g., using network device(s) 105). As in act 605, this could include causing a software component to present the result of the determining at a user interface.

In embodiments, method 800 includes ranking each subject section that was determined to be different than comparison sections in one or more of the comparison traces. For example, if a first subject section was different than all the corresponding sections the comparison execution traces, then the ranking/correlation component 117 e might rank this difference more highly (i.e., more important) than a second subject section that was different than less than all corresponding sections in the comparison execution traces. As such, method 800 might comprise assigning a ranking to each subject section determined to be different, the ranking being based on a number of the plurality of comparison replayable execution traces from which the subject section is different. Based on this ranking, in act 806, providing the indicia of the result of the determining might comprise instructing the software component or the other computer system to visually rank the one or more subject sections that are determined to be different at a user interface, based on a corresponding ranking for each of the one or more subject sections.

In method 800, each section can correspond to any grouping identified by the grouping component 115. Thus, for example, each section might correspond to a function, in which case each section corresponds to a sequence of one or more executable instructions that executed as a single function. In another example, each section might correspond to a sequence of functions, in which case wherein each section comprises a sequence of one or more related functions, each function corresponding to a sequence of one or more executable instructions that executed as the function. Similar to method 600, the comparing in act 804 can be based on group identity, function identify, function parameters, etc. Thus, comparing the subject replayable execution trace and the plurality of comparison replayable execution traces in act 804 could comprise comparing each of the plurality of subject sections against the one or more of the plurality of distinct comparison sections based at least on an identity of each section, comparing each of the plurality of subject sections against the one or more of the plurality of distinct comparison sections based at least on an identity of at least one function within each section, comparing each of the plurality of subject sections against the one or more of the plurality of distinct comparison sections based at least on function parameter information, etc.

FIG. 9 illustrates a flowchart of an example method 900 for diffing a plurality of subject replayable execution traces against a plurality of comparison replayable execution traces (i.e., an M:N diffing). Method 900 will now be described within the context of with FIGS. 1-8. While, for ease in description, the acts of method 900 are shown in a particular order, it will be appreciated that some of these acts might be implemented in different orders, and/or in parallel.

In embodiments, method 900 occurs in a similar manner to method 800, except that in method 900 different mappings of equivalent sections are identified for the subject execution traces in addition to the comparison execution traces, and different sets of distinct sections are identified for the subject execution traces in addition to the comparison execution traces. Then, these distinct sections are used on both sides of the comparison, and the transitive property is applied within both of the subject execution traces and the comparison execution traces.

As shown in FIG. 9, method 900 includes acts 901 a of accessing a plurality of subject traces and 901 b of accessing a plurality of comparison traces. These acts 901 could be performed serially or in parallel. In some embodiments, acts 901 comprise accessing a plurality of subject replayable execution traces, and accessing a plurality of comparison replayable execution traces, each replayable execution trace representing a corresponding sequence of executable instructions that executed as part of a corresponding executing entity. For example, similar to act 801 of method 800, act 901 can utilize the trace access component 114 a to access execution traces 113. However, in act 901, the trace access component 114 a can access two or more execution traces 113 as subject execution traces, as well as access two or more execution traces 113 as comparison execution traces. For instance, referring to FIGS. 7C and 7D, the trace access component 114 a might access two or more execution traces 113 for the left side of the comparison, and access two or more execution traces 113 for the right side of the comparison.

The debugging component 109 might utilize the alignment component 116 to align partial traces, such as is shown in the left and right sides of the comparison in FIG. 7D. Thus, in act 901, at least one of the plurality of subject replayable execution traces may be a partial subject execution trace, and/or at least one of the plurality of comparison replayable execution traces may be a partial comparison execution trace. When at least one of the plurality of subject replayable execution traces is a partial subject execution trace, method 900 might include aligning the partial subject execution trace with at least one other of the plurality of subject replayable execution traces. When at least one of the plurality of comparison replayable execution traces is a partial comparison execution trace, method 900 might include aligning the partial comparison execution trace with at least one other of the plurality of comparison replayable execution traces. In embodiments, aligning a partial subject or comparison execution trace with the at least one other partial or comparison replayable execution trace comprises applying at least one of a shortest common supersequence alignment algorithm (e.g., exact match component 116 a) or an approximate string alignment algorithm (e.g., approximate match component 116 b).

Method 900 also includes an act 902 a of identifying first mappings of sections among the subject traces that execute equivalently and 902 b of identifying second mappings of sections among the comparison traces that execute equivalently. These acts 902 could be performed serially or in parallel. In some embodiments, act 902 a comprises identifying a first set of mappings among the plurality of subject replayable execution traces, each mapping of the first set of mappings identifying two or more corresponding subject sections of consecutive executable instructions within the plurality of subject replayable execution traces that execute equivalently, each subject section in each mapping being from a different one of the plurality of subject replayable execution traces. For example, similar to how, in act 802 of method 800, the transitive analysis component 117 d analyzed comparison replayable execution traces to identify corresponding comparison sections that executed equivalently, in act 902 a the transitive analysis component 117 d can identify a first set of mappings among corresponding subject sections across the accessed subject replayable execution traces that execute equivalently.

In some embodiments, act 902 b comprises identifying a second set of mappings among the plurality of comparison replayable execution traces, each mapping of the second set of mappings identifying two or more corresponding comparison sections of consecutive executable instructions within the plurality of comparison replayable execution traces that execute equivalently, each comparison section in each mapping being from a different one of the plurality of comparison replayable execution traces. For example, act 902 b may occur in substantially the same manner as act 802 of method 800 to identify a second set of mappings among corresponding comparison sections across the accessed comparison replayable execution traces that execute equivalently.

Method 900 also includes an act 903 a of, based on the first mappings, identifying distinct sections in the subject traces and an act 903 b of, based on the second mappings, identifying distinct sections in the comparison traces. These acts 903 could be performed serially or in parallel. In some embodiments, act 903 a comprises, based on the first set of mappings, identifying a plurality of distinct subject sections within the plurality of subject replayable execution traces, each distinct subject section either (i) lacking a mapping in the first set of mappings, or (ii) being a representative subject section from a different mapping in the first set of mappings. For example, similar to how, in act 803 of method 800, the transitive analysis component 117 d used a set of mappings to identify distinct sections within the plurality of comparison execution traces to compare against sections in the subject execution trace, in act 903 a the transitive analysis component 117 d can use the first set of mappings to identify distinct sections within the plurality of subject execution traces to compare against distinct sections in the comparison execution traces.

In some embodiments, act 903 b comprises, based on the second set of mappings, identifying a plurality of distinct comparison sections within the plurality of comparison replayable execution traces, each distinct comparison section either (i) lacking a mapping in the second set of mappings, or (ii) being a representative comparison section from a different mapping in the second set of mappings. For example, act 903 b may occur in substantially the same manner as act 803 of method 800, by using the second set of mappings to identify distinct sections within the plurality of comparison execution traces to compare against distinct sections in the subject execution traces.

Notably, in act 903 a and/or 903 b, the transitive analysis component 117 d might choose less than all possible distinct subject and/or comparison sections. For instance, the transitive analysis component 117 d might initially choose to focus on sections that occur on more than one trace. In this case, the transitive analysis component 117 d might (at least in a first pass) select only representative sections from a set of mappings and skip sections that lack a mapping in the set of mappings. Thus, in act 903 a, the plurality of distinct subject sections might comprise less than all distinct subject sections within the plurality of subject replayable execution traces. In act 903 b, the plurality of distinct comparison sections might comprise less than all distinct comparison sections within the plurality of comparison replayable execution traces.

Method 900 also includes an act 904 of comparing each distinct section in the subject traces with the distinct sections in the comparison traces. In some embodiments, act 904 comprises comparing the plurality of subject replayable execution traces and the plurality of comparison replayable execution traces, including at least comparing each of the plurality of distinct subject sections against one or more of the plurality of distinct comparison sections. For example, similar to how, in act 804 of method 800, the differencing component 117 a compared subject sections from a single subject execution trace to distinct comparison sections from a plurality of comparison execution traces, in act 904 the differencing component 117 a can compare the distinct subject sections (i.e., identified in act 903 a) from the plurality of subject execution traces to the distinct comparison sections (i.e., identified in act 903 b) from the plurality of comparison execution traces.

Method 900 also includes an act 905 of, using the transitive property, determining a comparison status for each distinct section of the subject trace with the distinct sections in the comparison traces, and apply that status among mapped sections in the subject traces. In some embodiments, act 905 comprises, based on the comparing, determining a comparison status of each of the plurality of distinct subject sections, including determining at least one of whether each distinct subject section is (i) equal to at least one corresponding distinct comparison section, or (ii) different than the plurality of distinct comparison sections, wherein the determined comparison status of at least one particular distinct subject section with respect at least one particular corresponding distinct comparison section is applied to (i) each additional comparison section to which the at least one particular distinct comparison section is mapped in the second set of mappings, and to (ii) each additional subject section to which the at least one particular distinct subject section is mapped in the first set of mappings. For example, similar to how, in act 805 of method 800, the transitive analysis component 117 d applied a determined comparison status of a distinct comparison section to corresponding comparison sections in the comparison execution traces, in act 905 the transitive analysis component 117 d can apply a determined comparison status of a distinct comparison section to corresponding comparison sections in the comparison execution traces (i.e., based on the second mappings). In addition, however, in act 905 the transitive analysis component 117 d can also apply a determined comparison status of a distinct subject section to corresponding subject sections in the subject execution traces (i.e., based on the first mappings).

In act 905, a subject section might be different than a comparison section because it is a replacement, an insertion, or a deletion. Thus, in act 905, determining that a distinct subject section is different than the plurality of distinct comparison sections might comprise determining that the distinct subject section is at least one of a replacement of one of the plurality of distinct comparison sections, deleted from the plurality of distinct comparison sections, or inserted into the plurality of distinct comparison sections.

Method 900 also includes an act 906 of providing an indicia of a result of the determining. In some embodiments, act 906 comprises providing an indicia of a result of the determining to a software component at the computer system, or to another computer system. For example, similar to act 806 of method 800, in act 906 the output component 118 can provide an indicia of any of the differencing information produced by the diffing component 117 to a component at computer system 101, or to another computer system (e.g., using network device(s) 105). As in act 806, this could include causing a software component to present the result of the determining at a user interface.

In embodiments, method 900 includes, for a first group of subject sections across the plurality of subject execution traces, determining which differences between the first group and a second group of comparison sections across the plurality of comparison execution traces correlate highly with a subject section belonging to the first group. Based on these correlations, in act 906, providing the indicia of the result of the determining might comprise instructing the software component or the other computer system to identify one or more differences which correlate highly with a subject section belonging to a particular group.

In method 900, each section can correspond to any grouping identified by the grouping component 115. Thus, for example, each section might correspond to a function, in which case each section corresponds to a sequence of one or more executable instructions that executed as a single function. In another example, each section might correspond to a sequence of functions, in which case each section comprises a sequence of one or more related functions, each function corresponding to a sequence of one or more executable instructions that executed as the function. Similar to method 800, the comparing in act 904 can be based on group identity, function identify, function parameters, etc. Thus, comparing the plurality of subject replayable execution traces and the plurality of comparison replayable execution traces in act 904 could comprise comparing each of the plurality of distinct subject sections against the one or more of the plurality of distinct comparison sections based at least on an identity of each section, comparing each of the plurality of distinct subject sections against the one or more of the plurality of distinct comparison sections based at least on an identity of at least one function within each section, comparing each of the plurality of distinct subject sections against the one or more of the plurality of distinct comparison sections based at least on function parameter information, etc.

Accordingly, the embodiments described herein can diff a single subject execution trace against a single comparison execution trace (e.g., 1:1), can diff a single subject execution trace against a plurality of comparison execution traces (e.g., 1:N), and/or can diff a plurality of subject execution traces against a plurality of comparison execution traces (e.g., M:N). The embodiments herein operate by grouping sequences of related executable instructions, and performing diffing based on attributes of those groups to determine if the groups executed equivalently, even if the particular instructions in those groups differed. Thus, the embodiments herein can diff sets of traced instructions, even where those instructions executed from applications having different binaries (e.g., due code changes, compiler changes, compiler settings changes, processor ISA changes, and the like). In addition, the embodiments herein can diff different sections of traced instructions at different levels of detail, enabling processing resources to be devoted to those areas of particular interest.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the described features or acts described above, or the order of the acts described above. Rather, the described features and acts are disclosed as example forms of implementing the claims.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. When introducing elements in the appended claims, the articles “a,” “an,” “the,” and “said” are intended to mean there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 

What is claimed:
 1. A method, implemented at a computer system that includes at least one processor, for diffing a subject replayable execution trace against a plurality of comparison replayable execution traces, the method comprising: accessing a subject replayable execution trace, and accessing a plurality of comparison replayable execution traces, each replayable execution trace representing a corresponding sequence of executable instructions that executed as part of a corresponding executing entity; identifying a set of mappings among the plurality of comparison replayable execution traces, each mapping of the set of mappings identifying two or more corresponding comparison sections of consecutive executable instructions within the plurality of comparison replayable execution traces that execute equivalently, each comparison section in each mapping being from a different one of the plurality of comparison replayable execution traces; based on the set of mappings, identifying a plurality of distinct comparison sections within the plurality of comparison replayable execution traces, each distinct comparison section either (i) lacking a mapping in the set of mappings, or (ii) being a representative comparison section from a different mapping in the set of mappings; comparing the subject replayable execution trace and the plurality of comparison replayable execution traces, including at least comparing each of a plurality of subject sections of consecutive executable instructions within the subject execution trace against one or more of the plurality of distinct comparison sections; based on the comparing, determining a comparison status of each of the plurality of subject sections, including determining at least one of whether each subject section is (i) equal to at least one corresponding distinct comparison section, or (ii) different than the plurality of distinct comparison sections, wherein the determined comparison status of at least one particular subject section with respect at least one particular corresponding distinct comparison section is applied to each additional comparison section to which the at least one particular distinct comparison section is mapped in the set of mappings; and providing an indicia of a result of the determining to a software component at the computer system, or to an other computer system.
 2. The method of claim 1, wherein at least one of the plurality of comparison replayable execution traces is a partial trace.
 3. The method of claim 2, further comprising aligning the partial trace with at least one other of the plurality of comparison replayable execution traces.
 4. The method of claim 3, wherein aligning the partial trace with the at least one other of the plurality of comparison replayable execution traces comprises applying at least one of a shortest common supersequence alignment algorithm or an approximate string alignment algorithm.
 5. The method of claim 1, further comprising assigning a ranking to each subject section determined to be different, the ranking being based on a number of the plurality of comparison replayable execution traces from which the subject section is different.
 6. The method of claim 1, wherein providing the indicia of the result of the determining comprises instructing the software component or the other computer system to visually rank the one or more subject sections that are determined to be different at a user interface, based on a corresponding ranking for each of the one or more subject sections.
 7. The method of claim 1, wherein each section corresponds to a sequence of one or more executable instructions that executed as a single function.
 8. The method of claim 1, wherein each section comprises a sequence of one or more related functions, each function corresponding to a sequence of one or more executable instructions that executed as the function.
 9. The method of claim 1, wherein determining that a subject section is different than the plurality of distinct comparison sections comprises determining that the subject section is at least one of: a replacement of one of the plurality of distinct comparison sections; deleted from the plurality of distinct comparison sections; or inserted into the plurality of distinct comparison sections.
 10. The method of claim 1, wherein comparing the subject replayable execution trace and the plurality of comparison replayable execution traces comprises comparing each of the plurality of subject sections against the one or more of the plurality of distinct comparison sections based at least on an identity of each section.
 11. The method of claim 1, wherein comparing the subject replayable execution trace and the plurality of comparison replayable execution traces comprises comparing each of the plurality of subject sections against the one or more of the plurality of distinct comparison sections based at least on an identity of at least one function within each section.
 12. The method of claim 1, wherein the plurality of distinct comparison sections comprises less than all distinct comparison sections within the plurality of comparison replayable execution traces.
 13. The method of claim 1, wherein providing the indicia of a result of the determining causes the software component at the computer system to present the result of the determining at a user interface.
 14. A computer system, comprising: at least one processor; and one or more computer-readable media having stored thereon computer-executable instructions that are executable by the at least one processor to cause the computer system to diff a subject replayable execution trace against a plurality of comparison replayable execution traces, the computer-executable instructions including instructions that are executable by the at least one processor to cause the computer system to at least: access a subject replayable execution trace, and access a plurality of comparison replayable execution traces, each replayable execution trace representing a corresponding sequence of executable instructions that executed as part of a corresponding executing entity; identify a set of mappings among the plurality of comparison replayable execution traces, each mapping of the set of mappings identifying two or more corresponding comparison sections of consecutive executable instructions within the plurality of comparison replayable execution traces that execute equivalently, each comparison section in each mapping being from a different one of the plurality of comparison replayable execution traces; based on the set of mappings, identify a plurality of distinct comparison sections within the plurality of comparison replayable execution traces, each distinct comparison section either (i) lacking a mapping in the set of mappings, or (ii) being a representative comparison section from a different mapping in the set of mappings; compare the subject replayable execution trace and the plurality of comparison replayable execution traces, including at least comparing each of a plurality of subject sections of consecutive executable instructions within the subject execution trace against one or more of the plurality of distinct comparison sections; based on the comparing, determine a comparison status of each of the plurality of subject sections, including determining at least one of whether each subject section is (i) equal to at least one corresponding distinct comparison section, or (ii) different than the plurality of distinct comparison sections, wherein the determined comparison status of at least one particular subject section with respect at least one particular corresponding distinct comparison section is applied to each additional comparison section to which the at least one particular distinct comparison section is mapped in the set of mappings; and provide an indicia of a result of the determining to a software component at the computer system, or to an other computer system.
 15. The computer system of claim 14, wherein at least one of the plurality of comparison replayable execution traces is a partial trace, and wherein the computer-executable instructions also include instructions that are executable by the at least one processor to align the partial trace with at least one other of the plurality of comparison replayable execution traces.
 16. The computer system of claim 15, wherein aligning the partial trace with the at least one other of the plurality of comparison replayable execution traces comprises applying at least one of a shortest common supersequence alignment algorithm or an approximate string alignment algorithm.
 17. The computer system of claim 14, the computer-executable instructions also including instructions that are executable by the at least one processor to assign a ranking to each subject section determined to be different, the ranking being based on a number of the plurality of comparison replayable execution traces from which the subject section is different.
 18. The computer system of claim 14, wherein providing the indicia of the result of the determining comprises instructing the software component or the other computer system to visually rank the one or more subject sections that are determined to be different at a user interface, based on a corresponding ranking for each of the one or more subject sections.
 19. The computer system of claim 14, wherein the plurality of distinct comparison sections comprises less than all distinct comparison sections within the plurality of comparison replayable execution traces.
 20. A computer program product comprising one or more hardware storage devices having stored thereon computer-executable instructions that are executable by at least one processor to cause a computer system to diff a subject replayable execution trace against a plurality of comparison replayable execution traces, the computer-executable instructions including instructions that are executable by the at least one processor to cause the computer system to at least: access a subject replayable execution trace, and access a plurality of comparison replayable execution traces, each replayable execution trace representing a corresponding sequence of executable instructions that executed as part of a corresponding executing entity; identify a set of mappings among the plurality of comparison replayable execution traces, each mapping of the set of mappings identifying two or more corresponding comparison sections of consecutive executable instructions within the plurality of comparison replayable execution traces that execute equivalently, each comparison section in each mapping being from a different one of the plurality of comparison replayable execution traces; based on the set of mappings, identify a plurality of distinct comparison sections within the plurality of comparison replayable execution traces, each distinct comparison section either (i) lacking a mapping in the set of mappings, or (ii) being a representative comparison section from a different mapping in the set of mappings; compare the subject replayable execution trace and the plurality of comparison replayable execution traces, including at least comparing each of a plurality of subject sections of consecutive executable instructions within the subject execution trace against one or more of the plurality of distinct comparison sections; based on the comparing, determine a comparison status of each of the plurality of subject sections, including determining at least one of whether each subject section is (i) equal to at least one corresponding distinct comparison section, or (ii) different than the plurality of distinct comparison sections, wherein the determined comparison status of at least one particular subject section with respect at least one particular corresponding distinct comparison section is applied to each additional comparison section to which the at least one particular distinct comparison section is mapped in the set of mappings; and provide an indicia of a result of the determining to a software component at the computer system, or to an other computer system. 